In several heretofore commercially used pneumatically-applied spring-released brake assemblies or units, the piston rod is operatively connected to one end of a lever pivotally mounted intermediate its ends, and one end of a brake rod, that has a brake-hanger supported brake-shoe-carrying brake head pivoted to the other end, is operatively connected to the other end of this lever. One such brake unit is shown and described in U.S. Pat. No. 2,940,553, issued June 14, 1960, to George K. Newell et al, and assigned to the assignee of the present application. Brake assemblies, such as that disclosed in the above-mentioned Newell et al patent, are used to a considerable extent on railway passenger cars and in actual practice may have an overall height of as much as twenty inches or more. This type of brake assembly or unit cannot conveniently be employed on some of the newer types of light-weight railway and rapid transit passenger cars due to limitations of space provided by conventional mounting arrangements. Moreover, the tread brake unit disclosed in the patent to Newell et al is not provided with a so-called "snow brake" wherein the brake shoe is constantly pressed against the tread surface of a corresponding wheel with sufficient force whereby the heat generated thereby prevents the accumulation of snow and ice which would, as the result of freezing thereon, render this brake unit inoperative.
U.S. Pat. No. 3,837,443 issued Sept. 24, 1974 to Quentin T. Clemmons et al and assigned to the assignee of the present application, discloses a hydro-pneumatic brake unit that includes a so-called "snow brake" wherein the brake shoe is constantly pressed against the tread surface of a corresponding wheel to prevent the accumulation of ice and snow. In actual practice, a hydro-pneumatic brake unit constructed in accordance with the teachings of the Clemmons et al patent likewise has an overall height of approximately twenty inches or more. Consequently, this type of brake unit cannot conveniently be employed on some of the newer types of light-weight railway and rapid transit passenger cars due to limitations of space provided by conventional mounting arrangements.
Accordingly, it is the general purpose of this invention to provide a small, light-weight, compact pneumatic tread brake assembly that embodies therein a "snow brake" and delivers a braking force that is approximately four times that of brake units of approximately the same height and constructed in accordance with the teachings of the hereinbefore-mentioned Newell et al patent.
Moreover, this brake assembly delivers approximately 1.5 times as much braking force as a hydro-pneumatic brake unit constructed in accordance with the teachings of the Clemmons et al patent and has a height approximately one half that of the hydro-pneumatic unit.